part 1 The scapula operates within a very specific set of constraints that define how it can move. First, the acromion must always stay close to the clavicle because the AC joint forms a tight, stable connection between them. This joint acts almost like a pivot point, guiding most rotational movements of the scapula. Second, the inner surface of the scapula must stay flush with the rib cage. It can glide along it, but it cannot move into the ribs or drift too far away. This relationship ensures